The long-term goal of this project is to understand at the cellular level the mechanisms which control the interactions between peptidergic neurons and other cells. Neuropeptides have profound effects on many body tissues including the nervous system of most animals from lower invertebrates to humans. They perform a wide variety of physiological roles ranging from neurotransmitter to neurohormone. The nervous system of the moth, Manduca sexta, provides a particularly attractive model system in which electrophysiological, endocrinological, biochemical and developmental experiments can be performed conveniently in vivo and in vitro on individually identifiable peptidergic neurons. The cellular action of neuropeptides can therefore be followed with greater precision in this invertebrate system than in any present vertebrate preparation, where cellular studies on neuropeptides have proven difficult. The primary focus of this study will be 6 individually identified peptidergic neurons in the moth which contain two novel neuropeptides. We have previously shown that these two peptides, known as cardioacceleratory peptides (CAPs), play important cardioregulatory roles during adult emergence behavior in the moth. This proposal will utilize a multidisciplinary approach to examine electrophysiological and biochemical aspects of CAP function. Little is known about the electrophysiological mechanisms that regulate the activity of peptide-containing neurons. Intracellular recordings from active CAP neurons will be obtained during adult emergence behavior. In these experiments, electrical activity in individual CAP neurons will be directly related to the amount of peptide released. Additional experiments, in which the neuronal inputs to the CAP neurons are identified, will provide crucial new information on the neural control of peptidergic neurons and peptide release. The mode of action of the CAPs on their targets will also be explored. The electrophysiological effects of the CAPs will be studied in individually dissociated heart muscle fibers using conventional and voltage clamp recordings. The biochemical basis of CAP action on the heart will also be investigated by measuring CAP induced changes in the intracellular levels of cyclic nucleotides and/or inositol phosphates.